aircon + idle

[Matteh]

how does the ph1 172 cope with the added load of having aircon switched on at idle?

will it automatically sense the increased load and adjust the idle accordingly?

or is there some ECU trickery to keep it running right?

 

[DrR]

I'm guessing because of the cable throttle?

ph2 just drops revs lol, don't think it revs more.

 

[bmh.01]

The idle should be corrected to counter for the extra load of the a/c compressor, all of the 3 i've had did anyway. It may dip for a second or two but then it should pick back up to normal idle.

A Ph1 will use the ISCV to pick the idle up similarly as it would on cold start.

 

[Matteh]

so the aircon isnt run through the ecu?

how does it turn off on full throttle?

 

[bmh.01]

It doesn't turn off on full throttle and no it isn't ran through the ecu but the ecu has to authorise it before the a/c compressor clutch will engage.

Could explain but easier to post this, answers all the questions I think.
http://www.getflat.co.uk/pics/3286A-90.pdf

 

[Matteh]

thanks for that

so I need to wire in controls for engine speed, coolant temp and to allow 10s after ignition

I've also heard that AC shouldn't run when below 4deg?

 

[ditz]

its not linked to the ac as such - the ecu constantly trys to keep the engine running at a set rpm on idle.
so when you put aircon on the extra load brings the revs down so the idle control valve bypasses air and brings it back up.
try putting the car in first and very slowly disengage the clutch - for every bit you bring the pedal up it will constantly try to bring the revs back up to normal idle speed, then dip the clutch quickly it will rev right up

 

[Matteh]

brilliant!

thanks for your help!